Titanium 6Al-2Sn-4Zr-2Mo sheet material in various thicknesses, also known as Ti 6-2-4-2 sheet, is commercially available in a duplex annealed condition according to AMS 4919 specifications. According to AMS 4919 specifications, Ti 6-2-4-2 sheets under 0.1875 inches (4.762 mm) in nominal thickness are heated to 1650±25° F. (899±14° C.), held there for 30±3 minutes, cooled in air to room temperature, reheated to 1450±25° F. (788±14° C.), held there for 15±2 minutes, and then cooled in air to room temperature. In this condition, Ti 6-2-4-2 sheet is not very cold-formable, and a bend factor (bend diameter/sheet thickness) of about 12-14 T is generally required to reliably produce crack-free components with 90° bend angles.
Ti 6-2-4-2 sheets are commonly utilized to make gas turbine engine components such as nozzle sidewalls, flaps, ducts, cases, brackets, etc. Cold-forming such components from Ti 6-2-4-2 sheet is difficult, and often times, cracks are formed in such parts when they are cold-formed, resulting in poor production yields. Additionally, for successful cold-forming, bend radii need to be very large, which increases the weight of the part and reduces the stiffness thereof. Ti 6-2-4-2 sheet may be hot formed to tighter bend radii, but this requires expensive tooling and chemical milling after forming.
Therefore, it would be desirable to have improved techniques for cold-forming Ti 6-2-4-2 sheet material so that hot forming would not be required. It would also be desirable to have cold-forming techniques that allow better production yields than currently possible to be obtained when cold-forming Ti 6-2-4-2 sheet material. Furthermore, it would be desirable to have techniques that allow Ti 6-2-4-2 sheet components having 90° bend angles and bend factors of less than about 12-14 T to be formed via cold-forming without cracking.